Fogged, direct-positive silver halide emulsion containing a cyanine dye having a pyrazole{8 5,1b quinazolone nucleus

ABSTRACT

A photographic silver halide emulsion for direct positive use characterized by containing as a novel sensitizing agent at least one cyanine dye in which the 3-position carbon atom of the pyrazolo (5,1-b) quinazolone nucleus and the 1-, 2-, 3- or 4position of the cyanine heterocyclic nucleus thereof are linked with a methine chain (with the proviso that the linking is at the 4-position only when the cyanine heterocyclic nucleus is a quinoline or pyridine nucleus, and the linking is at the 1- or 3positions only when the cyanine heterocyclic nucleus is an isoquinoline). The photographic emulsion containing the above specific dye exhibits high light-sensitivity with less color retention defects.

United States Patent 1 1 I [111 3,868,256 Sato et a1. Feb. 25, 1975 1 FOGGED, DIRECT-POSITIVE SILVER I-IALIDE EMULSION CONTAINING A CYANINE DYE HAVING A PYRAZOLE[5, 1B]QUINAZOLONE NUCLEUS Inventors: Akira Sato; Akira Ogawa; Keisuke Shiba; Masanao Hinata, all of Kanagawa, Japan Fuji Photo Film Co., Ltd., Kanagawa, Japan Filed: July 16, 1973 App]. No.: 379,887

Assignee:

Foreign Application Priority Data July 14, 1972 Japan 47-70499 References Cited UNITED STATES PATENTS 9/1973 Bailey et al. 96/130 Primary Examiner-Norman G. Torchin Assistant ExaminerWon H. Louie, Jr.

Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A photographic silver halide emulsion for direct positive use characterized by containing as a novel sensitizing agent at least one cyanine dye in which the 3- position carbon atom of the pyrazolo [5,l-b] quinazolone nucleus and the 1-, 2-, 3- or 4-position of the cyanine heterocyclic nucleus thereof are linked with a methine chain (with the proviso that the linking is at the 4-position only when the cyanine heterocyclic nucleus is a quinoline or pyridine nucleus, and the linking is at the 1- or 3-positions only when the cyanine heterocyclic nucleus is an isoquinoline). The photographic emulsion containing the above specific dye exhibits high light-sensitivity with less color retention defects.

11 Claims, N0 Drawings FOGGED, DIRECT-POSITIVE SILVER HALIDE EMULSION CONTAINING A CYANINE DYE HAVING A PYRAZOLE[5, 1B]QUINAZOLONE NUCLEUS BACKGROUND OF THE INVENTION l. Field of the Invention The invention relates to a photographic silver halide emulsion, in more particular, to a direct positive silver halide emulsion which is sensitized with a dye containing a novel pyrazolo [5,l-b] quinazolone nucleus.

2. Description of the Prior Art It is known that when a photosensitive silver halide material is exposed to light including wave length where the photosensitive material is sensitive, the density increases as the amount of exposure increases until it reaches a maximum value, after which density begins to decrease if exposure further increases.

This phenomenon is called solarization. A similar reversal phenomenon (where the density lowers with an increase in the exposure dosage) also takes place, in the same way as seen in the case of exposure to light with a silver halide photosensitive material which has been optically or chemically fogged during the preparation of the silver halide emulsion.

Utilizing such a phenomenon, a positive image can be directly obtained.

The term silver halide emulsion for direct positive use" employed throughout the specification of this application means a silver halide emulsion so prepared as to directly form a positive image upon development after exposure to light (a positive light image).

There have been known a number of dyes as sensitizers for ordinary negative-use emulsions, such as, for example, monomethine cyanines, trimethine cyanines merocyanines, rhodacyanines etc. However, these known dyes cannot be used for the sensitization ofa silver halide emulsion for direct positive use without many defects such as flattening of the characteristic curve and rereversal (an increase in density after density has once decreased as exposure increases). 7

Moreover, almost all the dyes which have been hitherto known as sensitizers for silver halide emulsions for direct positive use have the defect that they cause color retention after the treatment of the photosensitive material. It is a serious defect in a photographic printing paper when such color retention occurs, For instance, in the case when these dyes are used as a sensitizer, it is impossible to obtain a high degree of whiteness in a black-and-white photographic printing paper, and color reproduction of high fidelity cannot be attained in the case of a color photographic material. The problem of color retention becomes more serious in hard tone photosensitive materials to be used, for example, as a lith type film, an X-ray photographic film or a copying film for microphotographyx It has been desired in the art that the dyes used for sensitizing direct positive emulsions should have no such faults and should not lower the maximum density of the picture image.

SUMMARY OF THE INVENTION Accordingly, the object ofthis invention is to provide a silver halide emulsion for forming direct positives which exhibits high sensitivity, and keeps a desired maximum picture image density with minimum color retention.

5 taining at least one cyanine dye in which the 3-position carbon atom of the pyrazolo [5,l-b] quinazolone and the 1-, 2-, 3- or 4-position of the cyanine heterocyclic nucleus thereof are linked by a methine chain, with the proviso that the linking at the 4-position takes place only when the cyanine heterocyclic nucleus is a quinoline or pyridine, and the linking at the lor 3-position takes place only when the cyanine heterocyclic nucleus is an isoquinoline.

DETAILED DESCRIPTION OF THE INVENTION Typical examples of the cyanine heterocyclic nuclei of the cyanine dyes employed in this invention include oxazoline nuclei, oxazole nuclei, benzoxazole nuclei, naphthoxazole nuclei, thiazoline nuclei, thiazole nuclei, benzothiazole nuclei, naphthothiazole nuclei, selenazole nuclei, 2-pyridine nuclei, 4-pyridine nuclei, 2-quinoline nuclei, 4-quinoline nuclei, l-isoquinoline nuclei, 3-isoquinoline nuclei, imidazole nuclei, benzimidazole nuclei, indolenine nuclei, imidazo(4,5- b)quinoxaline nuclei, pyrrolidine nuclei, etc.

These heterocyclic rings or benzene rings (with generally one or two benzene rings being present) in con densed heterocyclic rings may be substituted one or more substituents such as alkyl, aryl, hydroxyl, alkoxyl, carboalkoxyl or alkoxycarbonyl groups (for example,

.having from I to 8 carbon atoms preferably l-4 carbon atoms) nitrogroups or halogen atoms. Specific examples of these cyanine nuclei include, as thiazoles, for instance, thiazole, 4-methyl thiazole, 4-phenyl thiazole, S-(p-hydroxyphenyl)-thiazole, S-methyl thiazole, 5- phenyl thiazole, 4-(o-hydroxyphenyl)thiazole, dimethyl thiazole, 4,5-diphenyl thiazole, etc; as benzothiazoles, for instance, benzothiazole, 4- hydroxybenzthiazole, 7-fluorobenzothiazole, 4- chlorobenzothiazole, 5-chlorobenzothiazole, 6-

chlorobenzothiazole, 7-chlorobenzthiazole, 4-methyl benzothiazole, S-methyl benzothiazole, 6-methyl benzothiazole, 5,6-dimethyl benzothiazole, 5- bromobenzothiazole, 6-bromobenzothiazolc, 5- phenylbenzothiazole, 6-phenyl benzothiazole, 4-phenyl benzothiazole, 4methoxybenzothiazole. 5- methoxybenzothiazole, 6-methoxybenzothiazole, 7- methoxybenzothiazole, S-methoxycarbonyl benzothiazole, 5-iodobenzothiazole, 6-iodobenzothiazole, 4- ethoxybenzothiazole, S-ethoxybenzothiazole, 5- ethoxycarbonyl benzothiazole, tetrahydrobenzothiazole, 5-(N,N-dimethylamide)benzothiazole, 5,6-dimethoxybenzothiazole, S-hydroxybenzothiazole, 6-hydroxybenzothiazole, 5-carboxybenzothiazole, 5- nitrobenzothiazole, 6-nitrobenzothiazole, 5-chloro-6- nitrobenzothiazole, 5,6-dioxymethylene benzothiazole etc.; naphthothiazoles such as a-naphthothazole, ,B-naphthothiazole, B,B-naphthothiazole, S-methoxy-B- naphthothiazole, S-ethoxy-B-naphthothiazole, 7-methoxy-a-naphthothiazole, 8-methoxy-anaphtothiazole, 5-hydroxy-B-naphthothiazole, 7-hydroxy-a-naphthothiazole, 5-ethyl-B- naphthothiazole, etc.; oxazole such as oxazole, 4- methyl oxazole, S-methyl oxazole, S-phenyl oxazole, 4-(p-hydroxyphenyl)oxazole, 4,5-diphenyloxazole, 4- ethyl oxazole, 4,5-dimethyl oxazole, 4-phenyl oxazole, S-(m-hydroxyphenyl)-oxazole, etc.; bcnzoxazoles such 3-methyl quinoline, S-methyl quinoline, 7-methyl quinoline, 8-mcthyl quinolinc, -chloroquinoline, 8- chloroquinoline, 8-flu0roquinoline, 6- mcthoxyquinoline, -cthoxyquinoline, 6- hydroxyquinoline, 7-hydroxyquinoline, 8-

hydroxyquinoline, -nitroquinoline etc.; 4-quinolines such as quinoline, 3-methyl quinoline, 4-methyl quinoline, -5-methoxyquinoline, 6-methoxyquinoline, 7- methoxyquinoline, 8-methoxyquinoline, 6-methyl quinoline, 7-chloroquinoline, 8-chloroquinoline, 8-trifluoromethylquinoline, 6-nitroquinoline, etc.; 1- isoquinoline such as isoquinoline, 3-methyl isoquinoline, S-methyl isoquinoline, 7-methyl isoquinoline, 8- methyl isoquinoline, 6 -chloroisoquinoline, 6- methoxyisoquinoline, 8-methoxyisoquinoline, etc.; 3- isoquinolines such as 3-is0quinoline S-methyl isoquinoline, l-mcthyl isoquinoline, o-chloroisoquinoline, 6-

vmethoxyisoquinoline, 8-methoxyisoquinoline, etc.; in-

dolcnines such as indolenine, 3,3-dimethyl indolenine, 5-hydroxy-3,3-dimethyl indolenine, 3,3-dimethyl-6- chloroindolenine, 3,3,5-trimethyl indolenine, 3,3,7- trimethyl indolenine, 3,3-dimethyl-5-nitroindolenine, et.; Z-pyridines such as pyridine, 4-methyl pyridine, 6- methyl pyridine, 4,6-dimethyl pyridine, 4-butyl pyridine, 4-decyl pyridine, 4-octadecyl pyridine, 4,6 dibutyl pyridine, 4-benzyl pyridine, 4-phenyl pyridine,

4-( p-hydroxyphenyl )pyrid ine, 4,6-diphenyl pyridine,

4,6-dinaphthyl pyridine, 4-chloropyridine, 4- bromopyridine, 4,6-dichloropyridine,

chloropyridine, 4-bromopyridine, 6-bromopyridine, 4-hydroxy-pyridine, 4-methoxypyridine, 4- ethoxypyridine, 6-methoxypyridine, -ethoxypyridine, 4,6-dimethoxypyridine, etc.; 4-pyridines such as 4- pyridine, Z-methyl pyridine, 2-butyl pyridine, 2-decyl pyridine, 2-octadecyl pyridine, 2,6-dimethyl pyridine, 2,6dibutyl pyridine, 2-ben2yl pyridine, 2phenyl pyridiene, 2-(p-hydroxyphenyllpyridine, 2,6-diphenyl pyridine, 2-chloropyridin e, 2-bromopyridine, 2,6- dichloropyridine, Z-hydroxypyridine, 2- mcthoxypyridine, 2-ethoxypyridine, 2,6-

(limcthoxypyridinc, etc.; imiduzo- 4,5-b quinoxalines 4(p-hydroxyphenyU-thiazoline, etc.; 2-quinolines such as quinoline,

such as l,3-dicthylimiduzo-l4,5-hl-quinoxalinc, 1.3-.

diethyl-6-nitroimidazo-l 4,5 -b]-quinoxazoline, 1,3- diphcnylimidazo-l 4,5-b]-quinoxaline, 6-chloro-l,3- diphenylimidazo-[4,5-b1-q uinoxaline, l,3-diallyl imidazo-[4,5-bl-quinoxaline, etc.; oxazolines and imidazoles such as l-methylimidazol, l-methyl-4- phenylimidazol, etc; benzoimidiazoles such as benzimidazole, l-mcthyl benzimidazole, 5,6- dichlorobenzimidazole, l-cthyl-S- chlorobenzimidazolc, l-ethyl-5-nitrobenzimidazole, l-ethyl-5 ,6-dichlorobenzimidazole, l -ethyl-5- methoxycarbonyl benzotimidazolcs, etc.

Preferred cyanine dyes used in this invention are represented by any one of the following formulae (l), (ll) or (lll).

In the formulae, R and R each stands for an alkyl or substituted alkyl group, for example, having from 1 to 8 carbon atoms such as, for example, methyl, ethyl, propyl, isopropyl, n-butyl, n-pentyl, n-hexyl and like unsubstituted alkyl groups; B-hydroxyethyl, y-hydroxypropyl and the hydroxalkyl groups; B-acetoxyethyl, y-acetoxypropyl and like acetoxyalky groups; B-methoxyethyl, 'y-methoxypropyl and like alkoxyalkyl groups; B-carboxyethyl y-carboxypropyl, S-carboxybutyl, w-carboxypentyl and like carboxyalkyl groups; B-methoxycarbonylethyl, y-ethoxycarbonylpropyl and like alkoxycarbonylalky groups; ,B-sulloethyl. -y-sulfopropyl, y-sulfobutyl, 8-sulfobutyl and like sulloalkyl groups benzyl, phenethyl and like araryl groups; psulfophenethyl and like sulfoaralkyl groups; p-carboxyphenethyl and like carboxyaralkyl groups having one aryl ring and from I to 4 carbon atoms in the alkyl group; vinyl methyl groups; etc.

R stands for any one of the substituent groups which known for pyrazole [5,1-b]quinazoline compounds, such as a hydrogen atoms, an alkyl group (e.g., those having from 1 to 8 carbon atoms, such as methyl, ethyl, propyl, benzyl, etc.), alkoxyl group (e.g., those having from I to 8 carbon atoms, such as methoxyl, ethoxyl, etc.) carboxyl group or alkoxyearbonyl group (e.g., those in which the alkyl group has from 1 to 8 carbon atoms, such as methoxycarbonyl group, ethoxycarbonyl group, etc.), hydroxyl or aryl group (e.g., those monoaryl groups such as phenyl group, methoxyphenyl group, etc.)

R, stands for a hydrogen atom, an alkyl group (e.g., those having from 1 to 8 carbon atoms such as methyl, ethyl, propyl etc.), a cycloalkyl group (e.g., those hav ing from 3 to 8 carbon atoms such as cyclohexyl) or aryl group (such as a phenyl group).

L and L each represents a methine chain such as CH=, CR,,-- (wherein R stands for an alkyl group such as a methyl, ethyl, ethoxyethyl group; an aryl group such as a phenyl group etc., where L and R may be linked through a methylene chain to form, for example a 5 or 6 membered ring utilizing, e.g., 2 or 3 methylene groups).

Z stands for anatomic group necessary to form a cyanine heterocyclic nucleus, and particularly represents those mentioned hereinabove.

R stands for a substituent which is known for pyrazole [5,l-blquinazolone compounds, for example, a halogen atom (e.g., fluorine atom, chlorine atom, bromine atom, etc.), a lower alkyl group (e.g., those having 1 to 8 carbon atoms, such as methyl, ethyl, etc.), an alkoxy group (e.g., those having 1 to 8 carbon atoms such as methoxyl, cthoxyl, etc.), an aryl group (e.g., mono aryl groups such as a phenyl group, etc.), a carboxyl or alkoxycarbonyl group (e.g., those in which the alkyl group has from I to 8 carbon atoms such as methoxycarbonyl group; etc.), an acylamino group (e.g., those having from 2 to 8 carbon atoms such as acetylamino group, etc.), an amino group, nitro group, a phenoxy group, an alkylamino group e.g., those having from 1 to 8 carbon atoms, a sulfonic acid group, and the like.

The latter n represents to l, m-denotes 1 or 2 and p stands for l,2,3, or 4.

X* indicates an acid anion such as a chlorine ion,

bromine ion, iodine ion, thiocyanic acid ion, perchloric acid ion, p-toluene sulfonic acid ion, methyl sulfuric acid ion, ethyl sulfuric acid ion, etc.

Methods for the synthesis of cyanine dyes used in this invention will be explained in detail hereinbelow.

The dye represented by general formula (I) can be obtained by reacting the compound of the general formula (lV) (B): (I)) with a heterocyclic quaternary ammonium salt represented by the following general formula (V) (wherein R R and p each has the same meaning as previously defined in the case of the general formula (wherein Y denotes SR, Or" or NC5H5 OCH:

(R' and R" each denotes a methyl, ethyl or phenyl group), and R Z,L,,L n m and X each has the same meaning as previously given with respect to general formula (1)) under elevated temperature, e.g., about to C in ethanol in the presence of an organic base, e.g., 2.5 to 3 moles per mole of the compound of the general formula IV for about 30 to 60 minutes under normal pressures such as triethylamine.

The dye represented by general formula (I) can be prepared by reacting the compound of general formula (VI) which is obtained from the compound of general formula (III) by a Vilsmeiers reaction, with the heterocyclic quaternary ammonium compound of general formula (VII) (wherein R R Z, L L n and in each are the same as were previously defined for general formula (I)) in generally equimolar amounts in acetic anhydride at about 10 to 12 times by weight to the compound of the general formula VI at elevated temperature of about to C and under normal pressures for about 10 minutes followed by treatment with an alkali. The compound of general formula (I) can be also obtained in a smilar way by carrying out the above reaction in nitrobenzene at a temperature of about 150 to C and with the nitrobenzene being present in an amount of about 5 to 10 times by weight to the compound of the general formula IV in the presence of from about 3 to 4 mole of an organic base such as triethylamine per mole of the compound of the general formula (IV) fol lowed by treatment with alkali, instead of using acetic anhydride.

The dye represented by the general formula (II) can be obtained by alkylating the dye of general formula (I) with a conventional quaternizing agent as is generally used in the synthesis of cyanine dyes, for example, dimethyl sulfate, methyl-p-toluene sulfonate, propane sultone, butane sultone, an alkyl halide, etc,, at a 121.2 to 1:15 molar ratio and at a temperature of about 120 to 140C for about 20 minutes.

7 The dye represented by general formula (Ill) can be. obtained by reacting the compound represented by general formula (ylll) wherein R R R and p are each the same as defined for general formula (I)) with a heterocyclic quaternary ammonium salt as represented by general formula (VII) in acetic anhydride at an elevated temperature under conditions as described above the dye of the general formulae (l).

The compounds represented by general formulae (IV), and (VIII) can be synthesized by the procedures described in West German Pat. No. l,l20,455 and French Pat. No. l,282,8l9.

Typical examples of dyes used in this invention with their maximum absorption wavelengths ofin methanol are shown below. The maximum absorption wave length of dye (4) alone is, however, in solution in ethyl- (VIII) 15 ene glycol monomethyletheri CH3 N/ (lit) CHa-N i:

C H: C H CH1 max.

CHa-N Some specific examples for the synthesis of the dyes used in this invention are hereinafter described. All reactions conducted under normal pressures.

1. Intermediate 3-formyl-2-methylpyrazolo[5,l-b] quinazolone lnto 80 ml of dimethyl formamide there was dropwise added 40 ml of phosphorus oxychloride under ice cooling with stirring. A liquid suspension prepared by suspending g of 2-methylpyrazolo[5,l-b]quinazolone in 300 ml of dimethyl formamide was added thereto and the resultant mixture heated on a hot water bath for one hour to effect reaction. After cooling, the reacted liquid was added to ice-cooled water to thereby precipitate out crystals which were thereafter recovered by filtration. rinsed with water and dried to give pure white crystal ofthe titled intermediate compound having a melting poing above 300C.

2; Synthesis of Dye (2 l i. The reaction between 4.6 g of 2-acetanilide vinyl-3-ethylbenzothiazorium iodide and 2 g of 2- methyl pyrazolo[5,l-b]-quinoline was effected in 200 ml. of ethanol in the presence of 4 ml of triethylamine by refluxing under heating on a hot water bath for 1 hour. After the reaction was completed, the reaction product was concentrated by evaporating off ethanol and the dye which crystallized after cooling was recovered by filtration. Recrystallization of the resultant dye two times from a methanolchloroform solvent mixture herein about lzlby volume mixture was used throughout gave 2 g of the cyrstals ofdye (2) melting at 275C.

(ii). The reaction between 9.2 g of 3-ethyl-2-methylbenzothiazolium p-toluene sulfonate and 6 g of 3- formyl-2-methylpyrazole[5,l-blquinazolone was carried out in 120 ml of acetic anyhdride by refluxing the system at elevated temperature for 10 minutes. The crystals which separated were recovered by filtration and dried. The crystals obtained were dissolved in methanol under heating and a small amount of aqueous sodium hydroxide was added to separate out crystals which were thereafter recrystallized from a methanolchloroform solvent mixture to give 8.7 g of dye(2).

3. Synthesis of Dye (12) A mixture of 3 g of dye(2) and 3 ml of methyl-ptoluene sulfonate was heated to about to C for 20 minutes with melting to effect reaction. The crystals which separated after cooling were washed with ethyl ether and filtered to give the titled dye which was thereafter recrystallized twice from a methanolchloroform solvent mixture to give 23 g of dye(l2) melting at 262C.

Other dyes and dye intermediates than the above can be readily synthesized in a similar manner merely by varying the starting materials.

The emulsion for direct positive use of this invention preferably contains an organic desensitizer.

The organic desensitizer optionally used in this invention is a substance having the capability of trapping free electrons which have been generated in the silver halide grains upon irradiation with radiant energy, and which is absorbed in the silver halide. The organic desensitizer can further be defined as a substance having a minimum vacant electron energy sublevel which is lower than the electron energy sublevel ofthe conducting zone of the silver halide grains. Preferably, it is a compound having a maximum electron energy sublevel which is occupied which is lower than the valence electron zone of the silver halide grain. The measurement of the electron energy sublevels is complicated, but it is possible to determine it practically.

For instance, a determination for simple symmetrical cyanine dyes is reported by Tani and Kikuchi in Photographic Science and Engineering, Vol. 1 l (3), pp. 129 (1967), and determination on typical merocyanine dyes is reported by Shiba and Kubodera in International Congress of Photographic Science, 1970,

(Moscow), Preprint No.B-l2.

These electron energy sublevels are known to primarily correspond to the anodic polarographic half wave potential (Box) and the cathodic polarographic half wave potential (Ered).

A number of such organic desensitizers have been disclosed in, for example, US. Pat. Nos. 3,023,102; 3,314,796; 2,901,351 and 3,367,779, British Pat. Nos. 723,019; 698,575; 698,576; 834,839; 667,206; 748,681; 796,876; 875,887; 905,237; 907,367 and 940,152, French Pat. Nos. 1,520,824; 1,518,094; 1,518,095; 1,520,819; 1,520,823; 1,520,821 and 1,523,626, Belgian Pat. Nos. 722,457 and 722,594, and Japanese Pat. Publication Sho. 43-13167 and 43-14500.

Any of the above-mentioned organic desensitizers may be satisfactorily used in this invention. However, most desirable result are obtained using a desensitizing compound having a cathodic polarographic half wave potential (Ered) value of at least 1 .0 volt which is represented by the following general formula (X).

In the above formula (X), R stands for alkyl (e.g., having 1 to 8 carbon atoms) or allyl Z, X and In each has the same meaning as defined for general formula (1), and a is l or 2.

Typical examples of R include, for instance, a methyl, ethyl, butyl, hydroxyalkyl (e.g., hydroxyethyl), carboxyalkyl (e.g., carboxymethyl, 3-carboxypropyl) or sulfoalkyl group (e.g., 2-sulfoethyl) and the like.

Organic desensitizers used in this invention include, as typical examples, phenosafranine, pinacryptol yellow, S-m-nitrobenzilidene rhodanine, 3-ethyl-5-mnitrobenzylidene rhodanine, 3-ethyl-5-m-(2,4-dinitrobcnzylidene)rhodanine, S-o-nitrobenzylidene 3- phenyl rhodanine, l',3-diethyl-6-nitrothia-2'-cyanine iodide, 4-nitro-6-chlorobenzotriazole, 3,3-diethyl-6,6'-dinitro-9-phenylthiacarbocyanine iodide, 2-(p-dimethylaminophenyliminomethyl)- benzothiazole ethoetliyl sulfate, crystal violet, 3,3- diethyl-6,6'-dinitrothiacarbocyanine ethyl sulfate, l,3-diethyl-6-nitrothia-2- cyanine iodide, 1,3-diamino- S-methylphenazinium chloride, 4-nitro-6- chlorobenztrizaole, 3,3-di-p-nitrobenzylthiacarbocyanine bromide, 3,3'-di-p-nitrophenylthiacarbocyanine iodide. 3,3-di-o-nitrophenyl thiacarbocyanine perchlorate, 3,3'-dimethyl-9-trifluoromethyl thiacarbocyanine iodide, 9-(2,4-dinitrophenyl mercapto)- 3,3-diethylthiacarbocyanine iodide, bis(4,6-diphenyl pyrryl-Z-trimethine cyanine perchlorate, anhydrous 2- p-dimethylaminophenyliminomethyl-6-nitro-3-(4-sulfobutyl)benzothiazolium hydroxide, l-(2-benzothiazolyl)-2-(pdimethylaminostyryl)-4,6-diphenyl pyridinium iodide, 1,3-diethyl-5- 1,3-neopentylene-6- (l,3,3-trimethyl-2-indolinylidene)-2,4- hexadienylidene -2-thio barbituric acid, 2,3,5- triphenyl-ZH-tetrazolium chloride, 2-(4-iodophenyl)- 3-(4-nitrophenyl)-5-phenyl-tetrazolium chloride, 1-methyl-8-nitroquinolinium methyl sulfate, 3,6-bis 4- (3-ethyl-2-benzothiazolinidene)-2-butcnylidene -l ,2,4,5-cyclohexanotetron, etc.

The silver halide emulsion to be used in this invention includes, for example, emulsions of silver chloride, silver bromide, silver chlorobromide, silver iodochloride, silver iodochlorobromide and the like. Generally the sivler halide will be present at a level of from 1:2 to 2:1 by weight to the binder.

The grain size of such silver halides can be as are commonly used in the direct positive emulsion art, butespecially good results are obtained when the average particle size is included within the range of from 0.05 p. to 1.0 lL. The silver halide particles may be either reg ular or irregular, but most advantageous results are obtained when regular particles are employed.

Either single dispersion type emulsions or non-single dispersion type emulsions may be used in this invention, but the use of the former is preferred.

In general, an original emulsion to be used as a silver halide photosensitive material for direct positive use can be classified into one of the following two groups.

The first group of emulsions includes those having nuclei which can trap free electron in the interior of the silver halide crystal, the surface of which has been chemically fogged. The feature of this type emulsion resides in that it directly forms positive images by itself and is sensitized at its intrinsic absorption zone as well as having high sensitization by the spectral sensitization action due to the addition of a sensitizing dye. In this type of emulsion, the halogen composition of the silver halide should be such as to ensure easy combination between the interior of the silver halide and the chemical sensitizer or Group VIII metal salt employed for providing free electron trapping nuclei. Furthermore, the addition of the organic desensitizer serves to improve the degree of removal of highlights, especially for the prevention of re-reversal. In addition, the addition of bromine ions or iodine ions, e.g., of about 0.01 to 0.2 mole per mole of silver facilitates an increase in maximum density, in sensitivity and improve in highlight removal.

The type of original emulsion includes those which have no electron trapping nuclei inside the silver halide grains, the surface of the silver halide grains thereof having been chemically fogged.

This type of emulsion is a silver halide emulsion consisting of regular crystals, preferably of pure silver bromide, having no twin crystal plane and being as free of crystal defects as is possible.

This emulsion yields no direct positive image by itself. However, a direct positive image of high sensitivity can be obtained after an organic desensitizer has been adsorbed thereon.

Any of the above two types of original emulsions can be employed in this invention. The compound represented by the general formula (I) effectively sensitizes 19 either one of the above two types of original emulsions. The silver halide emulsions used in this invention are fogged by light or by a chemical treatment. Chemically fogged nuclei are formed by the addition reducing organic compounds such as, for example, hydrazine derivatives such as NH NH HCl or formaldehyde, thiourea dioxide, pounds, amine boranes, methyl dichlorosilane, etc.

Other methods of forming fogged nuclei which involve the use of a reducing agent in combinationwith metallic ions nobler than silver (e.g., gold ions, platinum ions, iridium ions, etc.) and further combinations of the reducing agent and the metallic ion with halogen ions.

The emulsion used in this invention mainly comprises gelatin as its protective colloid, and the use ofinert gelatin is especially advantageous.

If desired, however, all or part of the gelatin can be replaced with photographieally inert gelatin derivatives, water-soluble synthetic polymers (e.g., polyvinyl acrylate, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl alginate, carboxymethyl cellulose, hydroxymethyl cellulose, etc. The silver halide emulsion for direct positive use ofthis invention may further contain a variety of other additives commonly used in direct positive emulsions, e.g., a stabilizer for fogged nuclei (e.g., mercapto compounds, thione compounds, tetrazaindene type compounds etc.), highlight permeability improvers (e.g., stilbene type compounds, triazine type compounds ets.), optical brightening agents, ultraviolet absorbants, hardeners (e.g., chrome alum, aziridine compounds, epoxy-type compounds, mucohalogenic acid type compounds (halogen formyl, maleie acid type compounds ets.), coating aid (e.g., sodium polyalkylene sulfonate, saponin, anionic surface active agents having a betaine structure, antiseptic agents, plasticizers (e.g., polyalkyl acrylates, vinylic compounds such as a copolymer of an alkyl acrylate with acrylic acid, etc., polyalkylene oxide, etc.), color coupler and the like. They are merely used in their standard art proportions.

The amount of the dimethine dye or dyes used in this invention can not be generally defined since it depends upon the content of silver halide in the emulsion and upon the degree of surface area of the silver halide grain. However, the use of the dimethine dye in an amount ranging from 1 X to 2 X 10 mol per mol of silver gives particularly good results.

These dyes can be added as a solution in a Watermiscible solvent such as methanol, ethanol, ethylene glycol monomethyl ether, methyl ethyl ketone, acetone, pyridine. etc.

The dissolution of the dye can be facilitated by the application of ultrasonic vibrations.

Moreover, various methods which have been proposed for the sensitization of negative type emulsions,

for example, those disclosed in Japan Pat. Publications Nos. Sho. 44-23389, 44-27555, 44-22948, US. Pat. Nos. 3,485,634; 3,342,605; 2,9l2.343, German'Offenlegungsschrift No. l,947,935. etc. may be also employed.

polyamine com- Although the addition of the dye to the emulsion is conveniently carried out directly before coating, it may be effected during chemical ripening of and/or the formation of precipitates of the silver halide.

The amount of organic desensitizer or desensitizers cannot generally be defined since it varies depending upon the type of organic desensitizer used, but it is preferably in an amount ranging from 2 X 10 to 10 mol per mol of silver halide.

The emulsion of this invention can be applied any desired photographieally compatible support material to thereby produce a variety of photographic elements. The emulsion can be applied to one or both sides of the support which can be transparent or opaque. Typical supports used include cellulose nitrate film, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethylene terephthalate film and the other polyester films in addition to glass, paper, metal, wood, etc. Plastic resin laminated paper can also be employed.

The emulsion of this invention is suitably treated after exposure by known procedures for direct positive emulsions by treating it in a developing bath, fixing bath, stabilizing bath and the like baths, or at least one bath which combines such treatments.

The primary characteristic feature of this invention resides in sensitizing silver halide emulsions for direct positive use by employing a cyanine dye having a pyrazolo[5,l-b]quinazolone nucleus. The use of alkylated derivatives gives particularly high sensitivity.

The secondary characteristic feature of this invention is to provide a silver halide emulsion for direct positive use having a shapr maximum spectral sensitivity. In other words, the spectral sensitivity curve of the silver halide emulsion for direct positive use of this invention has a sharp cut-off at the long wave length side. Ac cordingly, a photosensitive material containing the emulsion of this invention is especially advantageous for handling under a safe light.

The third characteristic feature of this invention resides in that the cyanine dye containing pyrazolo[5,lblquinazolone nucleus exhibits a superior effect of not lowering the maximum density of the silver halide photographie emulsion.

The fourth characteristic feature of this invention resides in that substantially no reduction in maximum density during storage of the silver halide emulsion for direct positive use takes place.

The novel dimethine dye or dyes used in this invention not only have a number of outstanding characteristic features as mentioned above, but also enable an increase in the reversal sensitivity and high light permeability to be obtained by used in combination with the organic desensitizer.

The silver halide emulsion for direct positive use of this invention is especially suited not only for making hard tone photosensitive materials such as copying materials, but also for making relatively soft tone photosensitive materials such as microfilms, copying films and ray films. The emulsion of this invention may be also used in color photosensitive materials.

The silver halide emulsions for direct positive use of this invention are not further only useful for exposure with visibles light but also useful for irradiation with electron rays, X-rays, 'y-rays, etc.

The dye used in this invention can also be used for other photographic puroses, such as, for example, as a 'filter dye, irradiation inhibiting dye, antihalation dye,

etc.

This invention will now be more fully explained in detail by the following examples.

EXAMPLE 1 ln order to firstly prepare an original emulsion, the following four solutions were prepared according to the recipes given below:

is! Solution Inactive gelatin 8 g Aqueous potassium bromide solution lN) 5 cc Water (60C) 500 cc 2nd Solution Silver nitrate I g Water (60C) 500 cc 3rd Solution Potassium bromide 70 g Water (60C) 150 cc 4th Solution Inactive gelatin 75 g Water (60C) 300 cc The second and the third solutions were added at 60C to the first solution over a period of 50 minutes and the mixture subjected to physical ripening by standing at 60C for an additional 5 minutes. After the resultant solution was combined with cc of a 0.2 N solution of potassium iodide, the pAg was adjusted to 6.0 by adding a silver nitrate solution. Hydrazine (generally 1.5 cc of 0.1% solution per Kg of emulsion) and gold chloride (generally 1 cc of 0.1% solution per Kg of emulsion) were then added to the solution, the pH adjusted to 10 with an aqueous sodium hydroxide solution, and the solution further ripened for an additional 10 minutes by standing at 60C. The resultant solution was neutralized with citric acid and washed with water.

After re-melting the resultant product, the forth solution was added to form an original emulsion which contained silver halide grains having an average particle size of approximately 0.2 ,u. with a normal tetragonal system with a (100 face.

To samples of this original emulsion, a methanol solution of each dye as given in Table l was added and then a suitable amount of saponin cc of a 1% solution per Kg of emulsion) was added to give respective sample emulsions which were thereafter applied to cellulose triacetate films at a dried film thickness of about 5 ,u. to thereby form sample photosensitive films.

Each sample film was wedge-exposed to light from a tungsten lamp (2,854K) (1.000 lux, 10 sec.) and developed at 20C for 2 minutes with a developer liquid having the following recipe, fixed with an acidic hard film fixed and dried. The densitometry of the developed sample using a densitometer manufactured by Fuji Photo Film Co., Ltd, yielded the characteristic curve thereof. The results of measurement on sensitivity, maximum optical density (Dmax) and minimum optical density (Dmin) of each sampale are given in Table l.

The sensitivity is shown by the relative value of the reciprocal of the exposure dosage required for obtaining a density of (Dmax Dmin)/2.

Sodium carbonate monohydrate -Continued Potassium bromide 2 g Water to k .1000. .90

The composition was diluted with water at a ratio of 1:1.

TABLE] It will be seen from the results in Table 1 that the silver halide emulsion for direct positive use of this invention has a markedly high sensitivity, Dmax and also exhibits less color retention (i.e., less of the dye remaining after treatment).

EXAMPLE 2 An original emulsion was prepared as follows:

To a first solution (prepared by dissolving 10 g inactive gelatin. 5 cc of a 1N aqueous solution of sodium chloride and 500 cc of water by heating at 60C, there were added under stirring at 60C a second solution (prepared by adding 500 cc of water to 100 g of silver nitrate followed by heating at 60C) and a third solution (prepared by adding 300 cc of water to 35 g of sodium chloride followed by heating at 60C for dissolution) over a period of 20 minutes. After the addition had been completed, the resultant solution was ripened for 5 minutes by standing at 60C and thereafter a fourth solution (prepared by adding 200 cc of water to 14 g of potassium bromide followed by heating at 60C for dissolution) was added over 5 minutes while stirring. After ripening for 10 minutes by standing at 60C, the mixture was cooled, rinsed with water and heated again to effect dissolution. Then hydrazine and gold chloride (as described in Example 1) were added after the pH had been adjusted at 10, and the mixture was ripened at 60C for another 10 minutes followed by the adjustment of the pH thereof to 6.5 by the addition of citric acid. To this mixture. a fifth solution (prepared by dissolving g of inert gelatin in 300 cc water) at 60C was admixed to obtain original emulsion.

The average particle size of the silver halide grains thus obtained was approximately 0.15 it. To this original emulsion, 32 cc of a 5 X 10 mol per liter solution in methanol of pinaryptol yellow was added, and then a methanol solution ofa dye as shown in Table 2 added thereto.

The resultant mixtures were further combined with a suitable amount of mucochlorie acid (20 to 30 ml of 2% solution per Kg of emulsion) and saponine (20 ml of 1% solution per Kgof emulsion), and the emulsions so formed applied onto individual cellulose triacetate films at a dried thickness of about 2 ,u to thereby give sample photosensitive films.

Each sample film was wedge-exposed to light from a tungsten lamp (2,854K) (1,000 lux. 10 sec.) and developed at C for 3 minutes with a developer liquid having the following recipe and, thereafter fixed with an acidic hard film fixer and dried.

Composition of the developer liquid:

Composition of the developer liquid: Water (about 30C) Anhydrous sodium sulfite Paraformaldehyde Sodium bisulfite Hydroquinone Potassium bromide Water to make The dcnsitometry of the developed sample using a dcnsitometer manufactured by Fuji Photo Film Co., Ltd. yielded the characteristic curve thereof. The re- .sults obtained after measuring sensitivity, Dmax and Dmin as in Example 1 are given in Table 2.

As is seen from the results Table 2, the silver halide emulsion for direct positive use of this invention has high sensitivity and Cmax and also exhibits good highlight permeability.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is:

l. A silver halide emulsion for direct positive use comprising fogged silver halide grains and containing at least one cyanine dye in which the 3-position carbon atom in the pyrazole [5. l-b] quinazolone nucleus thereof and the 1-, 2-, 3-, or 4-position of the cyanine heterocyclic nucleus thereof is directly linked or linked by way of a methine chain with 2 or 4 methine groups, with the proviso that the linking at the 4-position being only when the cyanine hetcrocyclic nucleus is a quinoline or u pyridine nucleus. and the linking at the land 3-position being only when the cyanine hcterocyclic nucleus is an isoquinoline nucleus.

2. The silver halide emulsion of claim 1, in which pyrazolo[5,l-blquinazolone nucleus of the dye contains an alkyl group at the l-or 4-position thereof.

3. The silver halide emulsion of claim 1, in which the cyanine heterocyclic nucleus is a benzoxalzole nucleus, a benzothiazole nucleus, a benzoselenazole nucleus, an indolenine nucleus, a thiazoline nucleus or an imidazo [4,5-b]quinoxalinenucleus.

4. The silver halide emulsion of claim 1, in which the silver halide in the emulsion is chemically fogged.

5. The silver halide emulsion of claim 4, in which the silver halide is fogged with a reducing agent and a gold in which by weight of the silver halide grains have a particle size which is within 40% of the average particle size of the silver halide grain.

7. The silver halide emulsion of claim 1, in which the emulsion additionally contains an organic densensitlZel'.

8. The silver halide emulsion of claim 7, in which the organic desensitizer is a compound represented by the general formula (X):

wherein R is an alkyl group or an allyl group, Z is an atomic group forming a cyanine heterocyclic nucleus. X is an acid anion, m is l or 2 and a is a l or 2.

9. The silver halide emulsion of claim 1 in which the emulsion additionally contains a photographic coupler.

10. The silver halide emulsion of claim 1 in which the cyanine dye is selected from at least one of the group those represented by the general formulae (I), (II) and (lll):

wherein R, and R each represents an alkyl group. a hydroxy alkyl group, an acetoxyalkyl group, an alkoxyalkyl group, a carboxyalkyl group, an alkoxycarbonylalkyl group, a sulfoalkyl group, a aralkyl group, a sulfoaralkyl group, a carboxyaralkyl group or a vinyl methyl group;

wherein R represents a hydrogen atom, an alkyl group, an alkoxyl group, a carboxyl group, an alkoxycarbonyl group, a hydroxyl group or an aryl group; wherein R is a hydrogen atom an alkyl group, a cycloalkyl group or an aryl group; wherein L and L each represents a methine chain; wherein Z represents the atoms necessary to form a cyanine heterocyelic nucleus;

wherein R represents a halogen atom, an alkyl X is an acid anion.

group, an alkoxyl group, an aryl group, a carboxyl 11. A silver halide photographic material for direct group, an alkoxycarbonyl group, an amino group, positive use comprising a support having thereon the a nitro group, a phcnoxy group, an alkylamino silver halide emulsion of claim 1. group, or a sulfonic acid group; wherein n is (l or 1. m is l or 2, and p is l, 2, 3 or 4;

and l 

1. A SILVER HALIDE EMULSION FOR DIRECT POSITIVE USE COMPRISING FOGGED SILVER HALIDE GRAINS AND CONTANING AT LEAST ONE CYANINE DYE IN WHICH THE 3-POSITON CARBON ATOM IN THE PYRAZOLE (5, 1-B) QUINAZOLONE NUCLEUS THEREOF AND THE 1-, 2-, 3-, ,OR 4-POSITION OF THE CYANNINE HETEROCYCLIC NUCLEUS THEREOF IS DIRECTLY LINKED BY WAY OF A METHINE CHAIN WITH 2 OR 4 METHANE GROUPS, WITH THE PROVISO THAT THE LINKING AT THE 4POSITION BEING ONLY WHEN THE CYANINE HETEROCYCLIC NUCLEUS IS A QUINOLINE OR A PYRIDINE NUCLEUS, AND THE LINKING AT THE 1- AND A POSITION BEING ONLY WHEN THE CYANINE HETEROCYLIC NUCLEUS IS AN ISOQUINOLINE NUCLEUS.
 2. The silver halide emulsion of claim 1, in which pyrazolo(5,1-b) quinazolone nucleus of the dye contains an alkyl group at the 1-or 4-position thereof.
 3. The silver halide emulsion of claim 1, in which the cyanine heterocyclic nucleus is a benzoxalzole nucleus, a benzothiazole nucleus, a benzoselenazole nucleus, an indolenine nucleus, a thiazoline nucleus or an imidazo (4,5-b) quinoxaline nucleus.
 4. The silver halide emulsion of claim 1, in which the silver halide in the emulsion is chemically fogged.
 5. The silver halide emulsion of claim 4, in which the silver halide is fogged with a reducing agent and a gold compound.
 6. The silver halide emulsion of claim 1, in which the silver halide comprises fogged silver halide grains and in which 95% by weight of the silver halide grains have a particle size which is within 40% of the average particle size of the silver halide grain.
 7. The silver halide emulsion of claim 1, in which the emulsion additionally contains an organic densensitizer.
 8. The silver halide emulsion of claim 7, in which the organic desensitizer is a compound represented by the general formula (X):
 9. The silver halide emulsion of claim 1 in which the emulsion additionally contains a photographic coupler.
 10. The silver halide emulsion of claim 1 in which the cyanine dye is selected from at least one of the group those represented by the general formulae (I), (II) and (III):
 11. A silver halide photographic material for direct positive use comprising a support having thereon the silver halide emulsion of claim
 1. 